Wireless Power Design Kit - Medium Power - Review

Table of contents

RoadTest: Wireless Power Design Kit - Medium Power

Author: cybermah

Creation date: 15 Nov 2017

Evaluation Type: Development Boards & Tools

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: null

What were the biggest problems encountered?: It would be nice to have a way to program the device for prototyping. No sample source code.

Detailed Review:

Hi,

First I would like to thank ROHM Semiconductor and Element14 for giving me this chance to review the Wireless Power Design Kit.

I have to say this is probably the hardest review to do.  The kit is a really good product for demonstrating Wireless Power Design.  Right out of the cardboard box you can see that the product is well constructed.  It comes with everything you need to demonstrate how you can power a device without having to connect it directly to a power source.  The biggest issue with the kit in my opinion was there is no way out of the box to interface the load modules microcontroller to load new settings    If you really want to prototype with it you will need to remove the load module and attach it to another microcontroller using I2C protocol to adjust the settings.

Unboxing:

Block Diagram:

The block diagram show how the parts of the transmitter and receiver.  The interesting part about it, is the green communication line depicted in the image.  I couldnt figure out if the transmitter and receiver are actually communicating as there was very little information about it or is this just a feedback loop.

Schematics:

The ROHM site was kind enough to provide a download of the schematics, bill of materials layout and gerber files.

Transmitter Module.

Receiver Module

Load module

Testing:

The first test I did was to see how aligned the receiver module had to be on the transmitter base. With this test, I basically just place the receiver unit on the transmitter and moved it from center to each side and slowly lifted it off.   It looks like it has to be within approximately 5mm in any direction. which isn't too bad considering the size of the coils.  I would expect that if you needed a bigger area, you could use a bigger coil.

Powering up the device show that there is a little bit of noise on the output.  The power went to 10 volts and stayed there as long as the receiver was centred.

The power would stay at 10 volts until you move the receiver a little bit, I moved receiver until the load modules leds start to flicker, you can see that the voltage fluctuated a couple of volts but stayed between 8 and 10 volts.  It would stay there as long as it didn't move further off center and / or the transmitter doesn't go into error.  Once this happen, the transmitter stops transmitting power.

Something that I did notice was once the transmitter went into an error, it didn't reset itself until you remove the receiver module far enough away from the transmitter  It would be important to make sure an end product would have some mechanism to make sure the transmitter and  receiver stays aligned when used for powering or charging a device.

The product documentation states that the receiver module is designed with header so that different load modules could be stacked. what is important to know is the load module contains the microcontroller that controls the settings on the receiver.  If stack-able load modules are added only one module should contain the microcontroller and the other should purely be loads.

When it comes to a load module controller, this is where the product could make some improvements.  A developers package would be nice.  I was not able to find any sample code to create a custom load module.  I was able after a lot of searching find a document that outline the registers in the receivers module that could be used for programming, Here is the datasheet  

Conclusion:

I'm happy to have the opportunity to evaluate this product.  And it was one of the missing hardware design piece I needed for my wireless Geo tag I want to build.  Aside from the size of the coil, the circuit on the receiver module would definitely be small enough to work in my project.

I had a hard time doing an evaluation on this product for a couple of reason.

1. The product out of the box works as stated.  You plug in the transmitter and put the receiver on it and it transmits power.
2. Lack of a developers package.  It would be really nice to have some basic and advance sample code to program the receiver.  Although I did eventually find a datasheet that would help with this, there is a lot of registers to go though.

All in all, after studying the schematics, I would recommend using this design in my projects that require a wireless power option.  My only wish is that ROHM comes out with a developers document with some same source code.

Thanks.